Engine Fundamentals and Four-Stroke Cycle
Understand how a four-stroke engine turns fuel into usable torque by moving a piston through intake, compression, power and exhaust, and learn the role of each major component along the way.
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Safety notice
- Never open a cooling system or remove a radiator cap while the engine is hot; scalding coolant can escape under pressure.
- Gasoline vapour is highly flammable. Work in a ventilated area, keep ignition sources away, and never smoke near fuel.
- Do not rotate an engine by hand at the crankshaft bolt unless the manual says it is safe for that engine; some bolts are torque-to-yield and can fail.
- Treat ignition coils and injector circuits as live. Even with the key off, stored energy and capacitors can deliver a shock.
What you will learn
- Describe the four strokes: intake, compression, power and exhaust.
- Identify the major engine parts and explain what each one does.
- Explain how burning fuel is converted into mechanical energy at the crankshaft.
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Key points
- A four-stroke cycle needs two crankshaft revolutions to complete one power event per cylinder.
- The piston, connecting rod and crankshaft form the mechanical chain that converts linear motion into rotation.
- Valves and camshaft timing decide when air and fuel enter and when exhaust leaves.
- Compression raises temperature and pressure so the burn can do useful work instead of just making noise.
- Knock, misfire and low compression are the three classic families of engine-running faults.
All values shown are training examples. Real thresholds depend on the manufacturer, engine, temperature and system — always confirm with the vehicle service documentation.
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